Raymarine DSM250, Руководство пользователя

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Chapter 6: Sonar Mode Operation 6-3
Figure 6-1: Fish Indications
Effect of Frequency and Boat Speed
The return from a fish has a different appearance depending on
the frequency used: 50kHz produces a wide beam, so a fish spot-
ted by this frequency gives a broad arch; the 200 kHz beam is nar-
rower so the same fish produces a narrower arch.
The shape of the arch is also affected by the speed of the boat. If
the boat is moving slowly, the arches tend to be longer; if the boat
is moving more quickly, the arches are short and peaked. If the
boat is moving very fast, a fish may be indicated by vertical lines.
In Bottom lock mode the fish arches may appear distorted as the
bottom topography is removed from the image.
Bottom Indications
The bottom usually produces a strong echo, enabling the DSM250
to display great detail. The sounder module can indicate many dif-
ferent kinds of bottom conditions.
As illustrated in Figure 6-2 , a hard bottom appears as a thin line.
An arch-shaped image indicates a fish.
The same fish appears differently when shown by the
50 kHz or 200 kHz transducer beams.
A shallow arch is generated when the the boat is
moving slowly.
This indicates a group of small fish.
A fish moving under a stopped boat shows as a line.
When the boat is moving very fast, a fish appears as
two parallel lines.
D5017-2
50 kHz
200 kHz